The present invention relates to an apparatus for raising or lowering an outboard motor relative to the boat transom and, more particularly, to an improved power lift and latch apparatus for releasably holding the motor in its raised position and supporting the motor in its lowered position.
Marine propulsion devices, such as outboard motors, are supported from the boat transom by a mounting assembly. Outboard motors typically utilize a transom bracket for mounting the motor directly on the boat transom. Outboard motors mounted directly on the transom may usually be trimmed, either manually or with powered means, by pivoting the motor about a generally horizontal axis to position the propeller and optimize thrust with respect to the plane of the boat. However, the vertical position of the motor with respect to the boat cannot typically be changed beyond the somewhat limited amount which results from the trimming operation.
Another type of drive mounting assembly is one which is capable of selectively supporting an outboard motor in either a raised or a lowered position spaced aft of the boat transom. Many of these transom extension types of mounting assemblies are of the general type which include a pivotally connected quadrilateral linkage. Recently, transom extension mounting assemblies have become increasingly popular on high performance boats powered by outboard motors where a lower position of the motor improves initial boat acceleration and a higher position enhances top speed by reducing gear case drag. Additionally, a higher motor position reduces draft, thereby enhancing shallow water operation. It is further known that spacing the motor aft of the transom improves the handling characteristics of most boats at high speeds. These devices also allow the boat to have a higher transom for improved safety in following wave conditions and they also allow boat builders to manufacture a common hull and transom design for boat outboard and stern drive applications.
Examples of transom extension mounting assemblies for outboard motors which support the motor spaced from the transom are disclosed in the following U.S. Pat. Nos.: 2,782,744; 3,567,164; 3,990,660; 4,013,249; 4,168,818; 4,673,358; and 4,682,961. The first five of the foregoing patents disclose apparatus which is utilized to raise the motor vertically and the latter two patents describe apparatus which is utilized to trim the propeller and tilt the motor up and out of the water about a generally horizontal axis. More particularly, U.S. Pat. No. 3,567,164 discloses a pivotal quadrilateral linkage by which an auxiliary outboard motor is attached in a spaced relationship to the rear of a larger outboard motor used as a primary source of driving power. A mechanical lever arm is used to raise or lower the auxiliary outboard with respect to the main outboard motor and its selected vertical position is held by manually inserting a pin through aligned holes in a latch plate and one of the legs of the linkage. U.S. Pat. No. 4,013,249 describes an outboard motor mounting assembly including a four leg quadrilateral linkage to which is operatively attached a pressurized fluid cylinder to assist in the manual raising or lowering of the motor with respect to the transom. The assembly also includes a spring biased over-center mechanism which urges a slotted latching arm into engagement with a stud or pin on one of the legs of the linkage to hold the motor in either its raised or lowered position. U.S. Pat. No. 4,168,818 also describes a manually operated quadrilateral linkage for mounting an outboard motor spaced from the transom of the boat including a spring-biased latching arm having a slot within which travels a leg-mounted abutment pin to establish and hold the motor in its raised and lowered positions. Torsion springs are also used at the pivotal connections of the legs of the linkage to provide an assist to the manual lifting or lowering of the motor.
U.S. patent applications Ser. No. 092,168, filed Sept. 2, 1987 now U.S. Pat. No. 4,757,971, July 19, 1988; Ser. No. 100,216, filed Sept. 23, 1987 now U.S. Pat. No. 4,836,811, June 6, 1989; and Ser. No. 103,508, filed Oct. 1, 1987, now U.S. Pat. No. 4,836,124, June 6, 1989, all of which are assigned to the assignee of this application, disclose outboard motor transom extension mounting assemblies which utilize a quadrilateral linkage arrangement to raise and lower the motor with respect to the transom. The quadrilateral linkage comprises four pivotally connected links forming a collapsible linkage the movement of which effects vertical movement of the motor. Power to operate the linkage is preferably provided by a double acting hydraulic cylinder which operatively interconnects two of the links of the quadrilateral linkage to raise or lower the motor by extension or retraction of the cylinder. Of the foregoing pending U.S. application Ser. No. 103,508 discloses a quadrilateral transom mounting assembly with opposite arms of unequal length, the effect of which is to provide limited movement of the motor (i.e. rotation about a horizontal axis) simultaneously with the vertical lifting movement.
Powered transom extension mounting assemblies of the type described above are used principally with large outboard motors comprising the primary source of driving power. Transom extension mounting assemblies, particularly those utilizing a quadrilateral linkage, for small or auxiliary outboard motors are generally manually operated by the boat operator, sometimes with a spring or gas pressure lift assist. The mechanical latching apparatus utilized with such manually operated mechanisms has typically been complex and/or cumbersome to operate. In addition, the fully powered lift systems utilized with large outboard motors are too expensive and sophisticated to justify their use on smaller outboard motors where vertical operating position is generally not particularly important.
Nevertheless, it would be desirable to have a transom extension mounting assembly for smaller outboard motors which includes a power lift apparatus which is inexpensive and simple to operate. Certain operating conditions, such as shallow water operation or the presence of a shallow water obstacle, which may require the lifting of a large primary outboard motor, may also require the lifting of a small auxiliary motor. A small or auxiliary outboard motor may also have to be lifted for trailering, storage or while operating the primary engine. Such an auxiliary lift system should also have the capability of holding or maintaining the motor in its raised or lowered position without maintaining the fluid pressure in the power lift system.